pulse amplitude modulation

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Zeeus

Joined Apr 17, 2019
422
Please throw some light on this circuit
I know! even after author's explanation he still does not understand :( :(
dull brain : just returned to this site and daily read


if you look closely, the other page figure is visible

understand U1C, triangle wave across C8 how this affects output of U2A?
U2A has open-drain output author says : so ??

Enlighten Z
Thanks

Mod: Added a clearer circuit image.E
 

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Alec_t

Joined Sep 17, 2013
10,369
Here's what it looks like:
Capture.PNG
Think of Vmod as the supply voltage for this transistor stage. If the FET is switching on/off at the carrier frequency, the stage output (the FET drain) goes between 0V and Vmod, i.e it is a square wave with an amplitude =Vmod . If Vmod is varying at the modulation frequency, then that amplitude will be varying too.
 
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